correct prototypes for srandom(), rand() and srand().

value.

to avoid drops even on slow NICs.

is now gPXE-specific.  (The standard malloc() et al have been in stdlib.h
for a while).

Add free memory counter.

somewhat redundant, and also causes gas to complain when we include
the profiling code (which uses an i586 instruction).

needed now that performance is up.

anyone?

this saves around 70us per received packet (which is around 50% of the
overall packet processing time).

full-length PKB allocation.

almost everywhere else.

quota is 1.

other protocol won't work at the moment.

protocols by URI scheme.

Tidy up code

reflect the fact that they allocate and deallocate user memory (i.e.
things reached through a userptr_t).

of blocking on asynchronous operations, when that isn't an important
aspect of the code.

it as a fallback network device rather than an explicitly forced network
device.

Clear routing table entries before re-attempting DHCP.

exception rather than the rule; we may as well keep things clean for other
protocols.

will enable us to cascade async operations, which is necessary in order to
properly support DNS.  (For example, an HTTP request may have to redirect
to a new location and will have to perform a new DNS lookup, so we can't
just rely on doing the name lookup at the time of parsing the initial
URL).

Anything other than HTTP is probably broken right now; I'll fix the others
up asap.

handle something as convoluted as

  ftp://joe:secret@insecure.org:8081/hidden/path/to?what=is#this

return a static buffer.